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Re: [Discuss-gnuradio] argggg .. WBX Front end issues
From: |
Marcus D. Leech |
Subject: |
Re: [Discuss-gnuradio] argggg .. WBX Front end issues |
Date: |
Thu, 12 Apr 2012 20:19:20 -0400 |
User-agent: |
Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.24) Gecko/20111108 Fedora/3.1.16-1.fc14 Thunderbird/3.1.16 |
On 04/12/2012 08:11 PM, dave k wrote:
blew my second WBF front end after 1 day of wonderfull RX. I don't know how it
happend. I was using a few different types vhf and uhf omnis and yagi antennas,
everything seemed to be working fine. Now it can't hear hardly anything and the
typical strong noise signal in the center freq is back. Is it possible that
some of the equipment mounted on the antenna mast could be shorting it out? Or
is the WBX just so sensitive that a strong signal can blow it up? I have 2
Ubiquiti bulllet2HP's on the roof. One is clamped to the same mast as the UHF
omni that was connected the to WBX. They are 24V DC over the unused pairs. Im
really bummed out. Any recommendations or similar experiences ?
_______________________________________________
Unfortunately, LNAs are notoriously sensitive little princesses. The
new revs of the WBX have TVS diodes between the RF connector and the LNA,
which should reduce this problem, at the expense of a slightly poorer
noise figure. If the local field strength of RF on your roof is high,
enough
can couple in to damage the LNA. In those situations a limiter might
be needed, or even a stiff bandpass filter to keep stray RF fields that
are out-of-band with respect to your application out of the front-end.
There's a company online, summitsource, that sells in-line gas-discharge
surge arrestors for CATV/SATV use that I've used for protecting
LNAs in the past. Taken local lightning hits and survived, for what
it's worth. The arrestors are cheap--under $4.00 apiece as I recall, and
have 75-ohm connectors. About 0.3dB insertion loss.
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org